Compressor-unloading mechanism



M. RIESNER COMPRESSOR UNLOADING MECHANISM Filed Sept. 1, 1925 2Sheets-Sheet 1 Oct. 12 1926. 1,302938 M. RIESNER COMPRESSOR UNLOADINGMECHANISM Filed Sept. 1. 1925 2 Sheets-Sheet 2 19 i I 28 2 2e avw'emto'aPatented Oct. 12, 1926.

UNITED STATES 1,602,938 PATENT OFFICE.

MICHAEL RIESNER, F CINCINNATI OHIO, ASSIGNOR 'IO WORTHINGTON PUMP ANDMACHINERY CORPORATION, OF NEW YORK, Y., A CORPORATION OF VIRGINIA.

COMPRESSOR-UN LOADING MECHANISM.

Application filed September This invention relates to improvements incompressor unloading mechanism.

It is the especial object of the present in-- vention to provide acombined starting and pressure unloading mechanism for compressors whichshall be durable and reliable in operation, comparatively simple inconstruct-ion', and which may be used with advantage in compressingplants in which the compressor is belt-driven or direct-connected to aprime mover, such, for example, as an electric motor. While the improvedmechanism may be applied to either duplex single stage or duplex twostage compressors, as well as, compressors of other types, and obviouslymay be so associated with such compressors as to secure a balancedconstruction, for convenience of illustration preferred and modifiedforms of the invention have been shown as applied to but onedouble-acting compressor cylinder and its receiver. In its preferredform, the invention includes pressure operated valves arranged tocooperate with each other and a speed-controlled valve for varying thede-- livery of the compressor while running at normal speed, and forautomatically unloading the compressor on stopping so as to enable thedriving motor on starting up to attain approximately normal orsynchronous speed before the compressor takes up its load. Otherfeatures of the invention not specifically alluded to above will behereinafter fully described.

To enable the invention to be fully under stood, preferred and modifiedconstructions of the improved apparatus will now be described in detailin connection with the illustration thereof in the accompanyingdrawings, and the features forming the invention then be specificallypointed out in-the claims. In the'drawings Figure 1 is a side elevationof a compressor plant-embodying the invention in a preferred form asapplied to a double-acting compressor cylinder and its receiver;

Figure 2 is a similar view of the compressor cylinder and associatedapparatus on an enlarged scale and partially in section, and

Figure 3 is a side elevation, partially in section, showing a modifiedform of adetail feature of the apparatus.

Referring now to the drawings, and espe cially Figs. 1 and 2, 10indicates a doubleacting compressor cylinder with the usual 1, 1925.Serial No. 53,818.

piston arranged to work therein, although it Wlll be understood that theimproved ap-v paratus may be readily applied to single or double-actingcylinders and receivers thereupper end of the casing of a trigger valve21. The latter consists of a casing having a piston valve 8 thereinarranged to be depressed by fluid pressure against the tension ofspring 1. Enlargements 23, 22, on such piston 8 control ports 0, 0!,respectively, such ports in turn being connected by pipes 24, 25,respectively, with casings 26, 27 mounted on the cylinder casting. Theplungers 28 in the latter casings are arranged to be moved downward byfluid pressure against the tension of springs 2. At their lower endstheplungers 28 carry fingers 29 arranged, in the present case.- to coactwith the valve strips of suction valves 30, 31 of the type hereinafterreferred to, located, respectively, on the crank and.head ends of thecylinder shown, so as to completely or partially unload the compressorand also load the same in accordance with predetermined receiverpressures, as well as to secure complete unloading of the compressorcylinder when the compressor stops, as will be hereinafter more fullydescribed. The enlargement 22 of the valve 8 is provided with a smallpassage e, the purpose of which will also appear later. To the lower endof the casing of trigger valve 21 is connected pipe 32, which at itsother end is connected to the casing of a trigger valve 33 of well knowntype, such, for example, as disclosed in United States Letters PatentNo. 1,441,840, dated Jan. 9, 1923. The valve body 3 of this'triggervalve is normally held seated by spring 4. In the present arrangementthe casing of trigger valve 33 is provided with passages f, g, and avent h, the purpose of which will a pear from the description ofoperation creafter. The receiver connection to the trigger valve is byway of pipes 34, 35, the latter being a continuation of pipe 19 abovereferred to. The suction valves 30, 31, as well as the discharge valves36, 37, preferably and as shown, are of the strip type disclosed inUnited States Reissue Letters Patent No. 13,991, dated October 12, 1912,and United State Letters Patent No. 1,341,145. dated May 25, 1920,although valves of any other suitable type may be employed.

While the apparatus thus far described will function efficiently inaccordance with the description of operation hereafter given toautomatically unload the compressor cylinder as the compressor comes toa stop, so that in starting up the driving motor may\ attainapproximately normal or synchronous speed before compressing actionbegins. and will also automatically reduce the delivery of thecompressor when the receiver pressure. with the compressor running atmaximum delivery, reaches a predetermined point, means arranged toco-operate with such combined starting and pressure unloading mechanismare preferably provided so that the driving motor may be automaticallystopped and started in accordance with the demands on the receiver.\Vhile various devices of well-known construction may be employed forthis purpose, there is shown in Fig. 1, more or less diagrammatically,an arrangement which includes a connection 38 between the receiver and apressure regulator 39 of any well-known type. In the presentarrangement, however, the pressure regulator 39 is set to function so asto throw the main switch 40 controlling the electric circuit to thedriving motor, only when the pressure in the receiver rises slightlyabove the pressure required to throw the trigger valve mechanism 33.Thus, when the pressure regulator functions, the main switch 40 isopened thereby, the compressor thus shut down, the speed responsivemechanism and associated devices then functioning to completely unloadthe compressor. In the present arrangement, also, the pressure regulator39 is set to function on a comparatively slight drop .in the highpressure required to actuate it as above, so as to again close the mainswitch 40 and start the compressor driving motor. 1

A brief description of the operation of the preferred constructionwill-now .be given: In Fig. 2 the respective parts are shown in thepositions they occupy with the compressor running at normal speedanddelivermg the maximum volume of fluid to the receiver. Assuming thatwith the compressor thus'running at normal speed and delivering atmaximum capacity, the 're-. celver pressure rises to a point which maybe readily predetermined by adjustment of the trigger valve spring 4,such pressure,

plied through pipes 35. 34 to the trigger valve body 3, will force thelatter downward against the tension of spring 4 and thus shut offcommunication with vent h in the casing of trigger valve 33. Pressurefluid thus admitted to. the upper side of the valve body 3 will. by wayof passages f, g and pipes 32, 21. pass into the casing 26 of suctionvalve 30. depress the plunger 28 therein. and bring the fingers 29carried by such plunger into contact with the valve strips, therebyholding such strips off their seats and unloading the crank end of thecylinder. The delivery of the compressor is thus reduced one-half.Assuming. now, that the receiver pressure rises, it will, when slightlyabove that required to operate the trlgger valve as above described, beapplied by way of pipe 38 (Fig. 1) to pressure regulator 39, causing thelatterto throw main switch 4) and thus break the electric circuit tomotor 13, and thus stop the compressor. As this oz'curs, the pilot "alvepiston 16, being raised by the spring attached thereto and against thetension of which the piston 16 was depressed by the centrifugal forceapplied by the governor weights in operation, will place ports a, b incommunication with each other, so that receiver pressure, by way ofpipes 35, 19, ports a, b, above referred to, and pipe 20, will then beapplied to the piston 8 of the trigger valve 21, depressing such pistonagainst the tension of spring 1 and placing ports 0, (l in communicationwith each other. Receiver pressure will now be maintained in casing 26by way of pipes 35, 19, ports a, b, pipe 20, passage e in enlargement 22of the trigger valve 21 and pipe 24, instead of through the triggervalve 33 and the connections above referred to. At this time, also,fluid pressure admitted through the above connections and port (I andpipe 25 will be applied to the plunger 28 in casing 27, de-' pressingthe same and placing the head end of the cylinder in unloaded conditionin the same. wa) as described with reference to ,the crank end thereof.Both ends of the cylinder are thus unloaded as the compressor stops, andremain so until the driving motor is again started. As above stated, a

slight drop in receiver pressure below that which was necessary toactuate the pressure regulator 39 to stop the compressor driving motor,will cause such regulator to again functlon to close switch 40 andstartthe driving motor 13. As the compressor comes up to normal speed thepiston of the pilot valve is raised to the position shown, thusreleasing the pressure above the trigger piston valve 8 and permittingthe spring 1 there of to return the trigger piston valve 8 to theposition shown. This permits the escape to atmosphere, by way of portI). pipe 20, passage 0 in enlargement 22 of the piston apvalve 8, andpipe 25, of pressurefluid in casconnected to mg 27. If the pressure inthe receiver is suflicient, the crank end of the cylinder may remainunloaded until a further drop in receiver pressure occurs, but when thereceiver pressure reaches a point below that required to operate thetrigger valve 33-, the latter will be returned to its seat by spring 4,whereupon pressure fluid in pipe 32 and below enlargement 23 of thepiston valve 8 will pass to atmosphere by way of passage 9 and vent h.The parts are now as shown in Fig. 2. Another rise in receiver pressureto a predetermined point will again throw the trigger valve 33 to reducethe delivery as above explained, while a slight additional .rise inreceiver pressure will cause the compressor to again stop, as abovedescribed.

While the preferred construction above described will functionefficiently with either a belt-driven or direct-connected motor drivefor the compressor, the modified construction shown in Fig. 3 isespecially applicable to installations where the compressor isdirect-connected to a synchronous motor.

In the modification of Fig. 3, there is provided an upwardly openingcheck valve 41 in pipe 42, which latter at its lower end is port 6 inthe pilot valve casing 17 (Fig. 1). At its other end such pipe isconnected to the upper end of the casing of a trigger valve mechanism 43somewhat similar to that of Fig. 2, the piston of the trigger valvebeing normally held in the position shown by spring 5 and provided withenlargements 44, 45 arranged to control ports m, 12. Port m is connectedby pipe 46 and branches (not shown) with the casings 26, 27 of suctionvalves 30, 31 (Fig. 2). Port n is connected by pipe 47 to casing of atrigger valve mechanism 48 similar to that of Fig. 2. Pipe 49, leadingto the receiver, is connected to the casing of trigger valve 48, whichlatter, in the present showing, is provided with passages 0, p anda'vent r arranged to be controlled by the trigger valve body 6, whichlatter is normally held seated as shown by spring 7. The tension of thespring 7 may be readily adjusted so that the trigger valve will functionat a predetermined receiver pressure. In the pipe 42 there is provided aby-pass connection 50 around check valve 41,.a vent s beingprovided insuch by-pass connection for a purpose which will be hereafter explained.

When the electric motor is direct-connected to the compressor, it ispreferable to provide a time element between the moment when the pilotvalve starts to function to load the compressor and the moment when hecompressor takes up its load, so as to permit the motor to attainsynchronous speed before compressing action begins. This result issecured in the modified arrangement shown by setting the pilot'valve sothat it will start to function when about of the full speedof thecompressor has been attained, and this adjustment of the pilot valve, inconnection with the size of the vent s in by-pass connection 50, willdetermine the time which will elapse before the fluid above the pistoncasings 26, 27 of suction valves 30, 31 has escaped to atmosphere by wayof pipes 46, 47, passage p and vent r in the trigger valve casing 48,the latter vent being opened when the receiver pressure fallssufliciently to permit the spring 7 to return the trigger valve body 6'to its seat. Pressure fluid above the enlargement 44 of the valve 43 hasalso escaped to atmosphere by way of pipe 42. by pass 50 and vent s.VVitlf the parts in these positions a brief description of the operationof the modified construction will now be given: Assuming that thecompressor is running at normal speed and the receiver pressure rises toapoint which may be readily predetermined by adjustment of the triggervalve spring 7, the valve body 6 of the trigger valve is forced downwardagainst the tension of spring 7 by fluid admitted through pipe 49connected to the receiver, thus closing vent r by cutting offcommunication therewith through passage p. Fluid A thus unload both thehead and crank ends,

of the cylinder quickly. Assuming now that the compressor is permittedto run continuously while thus unloaded, a drop in receiver pressure toa point below that which was necessary to actuate the trigger valve asabove described will permit spring 7 thereof to return the trigger valvebody 6 to its seat, thus opening communication withvent r in the triggervalve casing. This permits escape of pressure in the casings 26, 27, byway of pipe 46, ports m, n, pipe 47, and passage p to atmosphere at thevent 1'. so that the compressor is automatically loaded while running atnormal speed. )Vhen the co1 n pressor is stopped, receiver pressureadmitted through pipes 35.19, and ports a, b, (Fig. 1) to pipe 42connected to the latter port. will. as in the case of Fig. 2, be appliedto the unloader valve piston. depressing the same until enlargement 44thereon exposes port m to the pressure above the piston, so thatreceiver pressure will be applied by pipe 46 and branches (not shown) tothe casings 26, 27 to unload the compressor as above described. Instarting up, the time element above referred to depends on the settingof the pilot valve so as to function when at about 90% of the full speedof the phere by way of pipe 42. The driving m0- tor is thus permitted toattain its synchronous speed before the piston of the trigger valve 43rises sufliciently to place ports m, 'nin communication with each otherand thus permit escape of fluid pressure from casings 26, 27 by way ofpipe 46, ports m, n, pipe 4.7, passage 79 and vent r in trigger valvecasing 48, as above described. A manually controlled switch for startingand stopping the compressor may be used with the modified arrangement ofFig. 3 or automatic stopping and starting means such as described withreference to Figs. land 2 may be employed to stop and start the motor.

, bination with a double acting. compressor at the desired pressures.

It will be understood that various changes in the construction andarrangement of the parts herein shown and described may be made, whilestill retaining the invention defined by the claims.

What is claimed is:

1. A combined starting and pressure unloader for compressors,comprising, in com bination with a compressor cylinder and its receiver,a valve on said cylinder, a fluid pressure operated device for operatingsaid valve to load and unload said cylinder, a fluid pressure connectionto said device, a speed-controlled valve arranged to control the latterconnection, and connections between the receiver and said deviceincluding pressure operated valves arranged in series to co-operate witheach other and the speedcontrolled valve to actuate said device tounload and load said cylinder at predetermined receiver pressures whilethe compressor is running and to unload and load said cylinder forstopping and starting.

2. A combined starting and pressure unloader for compressors,comprising, in combination with a double-acting compressor cylinder andits receiver, valves for opposite ends of said cylinder, fluid pressureactuated devicesfor operating said valves to unload and load saidcylinder, fluid pressure connections to said devices, a speed controlledvalve arranged to control the'latter connections,

I and connections between the' receiver and said devices includingpressure operated valves arranged in series to co-operate with eachother and the speed controlled valve to actuate one of said devices tounload and load one end of said cylinder at predetermined receiverpressures while the compressor is running and both of said devices tounload and load both ends of said cylinder for stopping and starting.

3. A combined starting and pressure unloader for compressors,comprising, in combination with a compressor cylinder and its receiver,a valve on said cylinder, at fluid pressure operated device foroperating said valve to load and unload said cylinder, a fluid pressureconnection to said device, a speed-controlled valve arranged to controlthe latter connection, connections between the receiver and said deviceincluding pressure operated valves arranged in series to co-operate witheach other and the speed-' controlled valve to actuate said device tounload and load said cylinder at predetermined receiver pressure whilethe compressor is running and to unload and load said cylinder forstopping and starting, and means controlled by predetermined receiverpressures for starting and stopping the compressor.

4. A combined starting and pressure unloader for compressors,comprising, in comcylinder and its receiver, valves for opposite ends ofsaid cylinder, fluid pressure operated devices for operating said valvesto unload and load said cylinder, fluid pressure connections to saiddevices, a speed controlled valve arranged to control the latteroperated valve being arranged to be opened at a predetermined receiverpressure and to cooperate with the first named pressure operated valveand the speed controlled valve to unload and load one end of thecompressor cylinder while the compressor is running at normal speed.

5. A combined starting and pressure unloader for compressors,comprising, in combination with a double-acting compressor cylinder andits receiver, valves for opposite ends of said cylinder, fluid pressureoperated devices for operating said valves to unload and load saidcylinder, fluid pressure connections to said devices, a speed controlledvalve arranged to control the latter connections, a pressure operatedvalve in said connection arranged to co-operate with thespeed-controlled valve to automatically unload both ends of saidcylinder under control of the compressor speed, an independentconnection between said pressure actuated a compressor, and ineanscontrolling said devices and the receiver including a pressure operatedvalve normally closing the latter connection, said last named pressureoperated valve being arranged to be opened at a predetermined receiverpressure and tomoperate with the first named pressure operated valve andthe speed controlled valve to unload and load one end of the compressorcylinder while the compressor is running at normal speed, and meanscontrolled by predetermined receiver pressures for starting and stoppingthe compressor.

6. A combined starting and pressure unloader for compressors,compris1ng,-in combination with a compressor cylinder and its receiver,a valve on said cylinder, a fluid pressure operated device arranged foroperacting said valve to unload and load said cylinder, a fluid pressureconnection to said device, a speed controlled valve arranged to controlthe latter connection, and connections between the receiver and saiddevice including pressure operated valves arranged in series tocooperate with each other and the speed controlled valve to actuate saiddevice to unloadand load the cylinder at predetermined receiverpressures while the compressor is running and to unload and load saidcylinder for stopping and starting, an electric motor arranged to drivesaid valve and pressure operated valve for the free transmission ofpressure fluid to and from said pressure operated valve for actuatingthe valve to load and unload the compressor, said connections and thepressure operated and speed controlled valves being arranged toco-operate with each other to delay loading relatively to the movementof the speed controlled valve.

8. In a compressor unloader, the combination, with the trigger valve 21,and a speed controlled valve and connections for controlling said valve"by the compressor speed, of triggervalve 33 and connections forcontrolling said valve by receiver pressure, and connections betweensaid trigger valves whereby the pressure fluid transmitted throughtrigger valve 33 is controlled by trigger valve 21, substantially asdescribed.

In testimony whereof, I have hereunto set my hand.

MICHAEL RIE'SNER.

